Controller for printing presses or the like



4 Sheets-Sheet l H. L. MCCLEERY ET AL :k I l l. O

March 23, 1937.

CONTROLLER FOR PRINTING PREssEsOR THE LIKEV Original Filed sept. 16, 1929 NNMMN R March 23, 1937. H. L.' MCCLEERY Er AL 2749661 CONTROLLER FOR PRINTING PRESSES 0E -THE LIKE Original Filed Sept. 16, 1929 4 Sheets-Sheet 2 OOOOQOOO O O OO March 23, 1937. H. MCCLEERY ET AL 2,074,661

CONTROLLER FOR PRINTING PRESSES OR THE LIKE original Filed sept. l1e, 1929 4 sheets-sheet 5 Wyk@ March 23', 1937. H. L. MCCLERY ET AL 2,074,661

CONTROLLER FOR PRINTING PRESSES OR THE LIKE I Original Filed Sept. 16, 1929 4 Shees-Shee'l. 4

Patented Mar. 23, 1937 UNITED STATES CONTROLLER FOR PRINTING PRESSES OR THE LIKE Harold L. McCleex-y, Downers Grove, and Allan J. Cline, Chicago, lll.;

said Cline said McCleery assigner lto Continuation of application Serial No. 392,801, September i6, 1929. This application April 25, 1934, Serial No. 722,392

10 Claims.'

The present application is a continuation of application Serial Number 392,801 ledSeptember 16, 1929. z

. Our invention relates to electric controller 5 systems, and has for its main purpose the provision of a controller particularlyadapted for newspaper printing presses of the unit type in which a plurality of motors are employed for driving the units and folders which are ordim narily arranged in a continuous row and are divisible into groups forming presses of desired capacity.

'I'he control provided by the invention is well suited, though not limited, to the type of press 1.', drive shown in Patent No. 1,734,077, to Allan J. Cline, in which individual motors are provided for the several printing units and folders of the press.

An important object ofthe invention is to prow vide a device for facilitating the transfer from high to low voltage when the press is slowed down. As will later appear, a high voltage is used for normal running and a much lower voltage for certain occasions, such for example, as

. ,3 when the cylinders are being plated or when the web is being threaded through the press. After dropping out the high voltage contactor in slowing down, the drive motors for a time may continue to run fast enough to generate a coun- 30 ter E. M. F. of higher voltage than that of the low voltage circuit and if the transfer to the low voltage circuit were made under such conditions, serious damage might be caused such as short circuiting the' motors through the low volt- 33 age generator and causing excessive regeneration which might cause damage to the press, or, in any event break the Webs. The device above referred to'prevents the closing of the low voltage circuit until the counter E. M. F. generated 40 by the motors is reduced to substantially the E. M. F. of the low voltage line.

A further object of the invention is to provide in a control system of this character a novel means for dynamic braking.

.A still .further object of the invention is to provide in conjunction with the master switch which ls employed for controlling all the motors, means for interlocking the master switch and stop relay, thus insuring that the switch arm ,',0 will be returned to the oi! position in all cases after operation of the stop relay before any units of the press can again be` moved. This is an important safety feature, as will later appear. 'Various other objects and advantages of the 7,', invention will be apparent as it is better understood from the following description, which, taken in connection with the accompanying drawings, discloses a preferred embodiment thereof.

Referring to the drawings: r

Figure l is a diagrammatic view, illustrating a printing press and control devices therefor embodying our invention;

Figure 2 is a diagrammatic view of a master panel for controlling the press, the same being shown in rear elevation;

Figure 3 is a straight line wiring diagram for the master panel;

Figure 4 is a diagram of the same type illustrating the connections to the motors Aof two press units;

Figure 5 is a similar diagram illustrating the necessary circuit for commutating the individual motor fields to the exciter generators of the master control panels; and

Figure 6 is a diagram illustrating the connection of the push buttons and the commutating thereof to either one of the master panels.

To illustrate our invention we have shown on the drawings a diagram of the preferred control arrangements and devices for operating a newspaper printing press, the printing units of which are numbered i to 1 inclusive and the folder units of which are numbered FI and F2 in Fig. 1, diagrammatic illustrations oftwo master panels Il and l2, and suitable connections for connecting the master panels to the press.

The units I to 'l may be a part of the series of the printing units of the press and Aare each provided with a driving motor Il. 'I'he folders Fl and F2 are similarly provided with driving motors I5. Wires for controlling the motors I4 and i6 communicate with junction boxes I6, through suitable conduits Il. Push button outlets l8, which may be mounted adjacent or on each of the press units also communicate electrically with the junction boxes i6 through a conduit II. All of the electrical connections to the motors il and push button outlets i8 communicate with a switch box 22 through a conduit 2i. The switch box 22 may contain any type of tumbler or multiple switch, or may contain individual switches for directing the various circuits to the master panels. In the present instance we have shown two master panels and in this embodiment double throw switches are required to direct the current either through conduits 23 for connection with the master panel H, or conduits 24, for connection with the master panel l2. A high voltage line 25, which in the present instance is a `23() volt line, and a' low/l voltage line 26, which in the present instance is( a 4.0 volt line, communicate with bothof the master panels.

Motor generator sets 18, 19 hereinafter described, -are connected r respectively into Athe master.` panels II and I2 as diagrammatically shown in Fig. 1.

pf one lfolder and a selected number of press units,

together with their individual drive motors, and a main control station, and the operation of such a press may be controlled from a single pushbutton station, as the station I8, associated with the folder of the press.

As shown in Fig. 1, any individual press may be .controlled from either of two main control' stations to provide for emergencies such as a mishap to the electrical apparatus of one of ,thel

control stations, but when operating, .each press includes but one folderfand one main control station, as above described. v l

. Each master panel will preferably consist of an upper section or master switch section 32, a lower or-main control section 33 and a terminal board 33' (Fig. 2). The upper section 32 supports a motor operated face plate or master switch 3|, a stop relay 34, two poles 35 up, and one pole 36 down, a low voltage relay 31, two

poles 38 up, and one pole 39 down, a slow relay 4|, two p'oles 42 up, a paster relay 43, two poles 44 up, a generator voltage relay 45, single pole 46 up, an inch relay 41, single pole 48 up, an increase relay 49, singlepole 5I up, a decrease relay 52, single pole 53 up, a safe relay 54; single pole 55 down, a three-point paster dial switch 56, and

a three-point torque switch 51.

The lower section or main control panel 33 has mounted thereon a high voltage or 230 volt line contactor 58, two poles 59 up, two interlocks 60,

and an interlock |38; also alow voltage or 40' volt lline contacter 6|, two poles 62 up, and two interlocks 63; three accelerating contactors 64, single pole 65 up; a dynamicbraking contacter 66, single pole 61 up with normally open full field interlock |00; a transfer relay 68, a slow down contactor 68, single pole 10 up, and double pole line knife switches 1I and 12. All of the above mentioned devices are electrically interconnected as will 'be later described. The apparatus mentioned above is also illustrated by a straight line diagram, Fig. 3, with corresponding numerals.

Fig. 4 shows two of the individual unit motors I4, resistance elements 13, 14, and 16 for each motor, series field windings 16 and 11, and double throw switches 80, for connecting the respective motors .with either one of the master panels II or I2 showninFig. 1. Y

In Fig. 5 an exciter motor generator set is shown, the motor being indicated at 18 and the generator at 19. Shunt eld windings 8| and 82 for the individual drive motors I4 and I5 are connected as shown in Fig. 5, and double pole switches 83 are employed to associate said eld amasar '.1

windings 3| and 82 with the motor generator set 18, 19 of one or the other of the master panels II or I2.

In Fig. 6 the usual push buttons required for operation of the printing press are indicated and include a paster, button 84, a safe-run liut-A ton 85 having a circuit closing push button for preventing press operation and a circuit open'- ing push button for permitting press operation, said two last mentioned push buttons being mechanically inter-connected, a stop button 86, a

vdecrease button 81, an inch button 88, and an in.

crease button 89. Double throw switches are` included in the circuits with the above mentioned push buttons to provide a means of connecting them with either of the master control panels. The switches 80, 83 and 90, indicated in Figures 4, 5, and 6, are all preferably mounted in the switch box 22 (see Fig. 1) ofv the press unit controlled thereby. A

As previously -statedthe motor operated face plate 3| of the master control panels controls the sequence of certain relays and contactors and 'I4 and I5, which are connected in parallel so :.1

that each individual motor will have the correct i'leld strength for parallel operation at any desired speed. This makes Yiii-possible toomit a field rheostat formerly required on eachindividual motor and facilitates complete control of the individual motors by the master switch.

In the diagram we have shown all of the circuits on the master panel with the' apparatus` positioned ready for the starting 'of the press and with the line switches 1I and 12 open. The arm |0I of the master'switch 3| in starting position rests on contacts |02, |03, |04, and |05, but is shown in Fig. 1 as moved therefrom for the sake of cleamess. Said arm is adapted to be moved in a counterclockwise direction (viewing Fig. 2) ,for starting and speeding up the operation of the press, and in a clockwise direction for. slowing down or stopping the press. The actuating means illustrated is a small split eld motor |06, the shaft of whichcarries a pinion |01, which meshes with a gear |08 on a shaft I 09, which may be mounted in any suitable bearings and is connected to and adapted to transmit motion imparted to the gear |08 by the motor pinion, to a worm III, engaging aworm gear a GII `eld. of the generator 19 'to Y. When the generator voltage builds up, relay coil 45, which,is

thepress in manner which willhereinafter appear. With the master switch arm |0| in the 'motor circuits of the press units.

normal or off position, the control mechanism is in condition to operate the press for inching from X through the lower contact 38 of the low voltage relay,` through the coil of said relay to I03a, through stop relay contacts 36 to Y, thus making it possible to move arm IOI off the reset segment |04 without deenergizing low voltage relay 31. The back contact 55 of the safe relay 54 is closed, and depression of the inch button 88 (Fig. 6) will close a circuit from X through contact 55 to I0 through the inch button 88 to 222, through the high voltage or 230 volt interlock 60 to 20, through the low voltage or 40 volt line coil 6I to I1 through contacts II4 of relay |31 to I8, through one pole 38 of the low voltage relay 31 to I9, and through contact 46 of generator voltage relay 45 to Y, for energizing the Release of the inch button opens this circuit and deenergizes the motor circuit.

Current is supplied to the armature oi press motor I4 from on thelow voltage line 26 to 2, through contacts 6,2 of the low voltage contactor to Si, through series iield resistances 16, 11, to the armature, then through resistances 13, 14, 15 to R, then through the other contacts 62 of the lowvoltage contactor to 4, and then through knife switch 12 to on the low voltage line 26. Similarly, current is supplied to the armature of motor I4 from on the high voltage line 25 to'X, thence through the upper of the contacts 59 of the high voltage contactor to S4, thence through series eld resistances V16, 11, to the armature of motor I4, thence through resistances 13, 14, 15 to R, thence through the other contacts 59 of the high voltage contactor to Y, and thence Pressing the increase button 89, closes the increase circuit from X to 80 through relay 48 to 8| through a protective resistance I|5 to 82,

through an increase limit switch |I6 to I8,

through the low voltage contact 38 of relay 31 to I9 and the generator voltage contact 46 of relay 45 to Y. The closing of this circuit closes contact from X to 15, which energizes an increase field winding |I1 to 16 of the pilot motor |06 to Y, which rotates the master switch arm |0| in a counter-clockwise or press-accelerating direction, effecting the necessary connections for increasing the speed ofthe press.

Forward movement of the master switch arm IOI makes contact with a segment I2I, closing the inch button circuit of the press, which closes the low voltage main line contactor 6I, X to |2I through contact 60 to 20 through coil 6I to I1 through contact II4 to I8 through pole 38-oi relay 31 to I9, through contact 46 of generator relay 45 to Y, starting the press at slow speed, and by contact with a segment |22, closes a circuit through the 40 volt interlock 63 to 23, through the coil of the 230 volt line contactor 58 to I8, through the low voltage contact 38 of relay r31 to I9 and generator voltage-contact.46 of relay 45 to Y which closes the 230 -volt line contactor and thereby energizes the individual motors of the press units subject to the series resistance elements 13, 14, and in the armature circuit 7.-, of the motors |4 and I5 (Figs. 3 and 4). The

line contactors 58 and 6| are preferably electrically and mechanically interlocked to insure against the closing of both at any instant to avoid danger of a short circuit. As the master switch arm I0| moves forward, contact is made successively with segments |23, |24, and |25, closing the contacts 65 of the accelerating contactors 64 successively, thereby cutting out the resistance elements 15, 14, and 13 in the order mentioned, thus bringing the individual motors I4 and I5 up to their full field speed. Further movement of the arm |0| brings it into successive contact with contact buttons |26, one of which isconnected to a segment |21 and the remainder of which are connected together through suitable resistance elements, together forming a step-up resistance |28 (Fig. 3). As the arm |0| makes successive contact with the buttons |26, it decreases the iield voltage of the exciter generators 19 and in turn the field excitation of the unit motors I4 and I5, and further increases the operating speed of the press as the arm |0I advances.

Depression of the decrease button 81 closes a circuit from X to 10 through a decrease limit switch |29 to 13 and the decrease relay 52 to Y.

` Operation of the decrease relay 52 in turn closes a circuit through its contact 53 from X to 80 and a decrease winding I3| to 16 of the pilot motor |06 to Y, thereby causing a reversal of the direction of movement of the arm IOI and the dropping of all the connections established in the forward movement thereof.

The pilot motor |06 is preferably a motor of the split field type or a motor having a eld winding adapted to cause rotation of the motor in one direction corresponding to the iield winding III, and a second eld winding adapted to cause rotation of the motor in the opposite direction corresponding with the winding I3| (Fig. 2).

A segment of the master switch 3| is provided with a sliding contact member II8, having. a iiexible wiper ||9 extending into the path of the arm |0I (Fig. 2). The member ||8 is manually Yadjusted on the segment |20 to a position determined by a running test, at which the press operates with the greatest efciency and without undue danger or strain. When the arm |0| makes contact with the wiper |I8, it shorts out the increase relay coil 49 and stops the pilot motor |06 by the circuit X on arm IOI to 8| on contact I|9 through protective resistance II5 to 82 through limit switch |I6 to I8 through contact 38 to I9 through generator contact 46 to Y, thus stopping acceleration and preventing further control of the press through the increase button, the short being made through the protecting resistance II5 (Fig. 3).

The depression of the stop button 86 closes X to 30, operates the stop relay 34, and closes a circuit through a coil |32 of said stop relay to 3Ia, through a protective resistance |33 to Y. The closing ofthis circuit actuates the stop relay 34 which establishes its own holding circuit through one of the poles 35, in closing, the circuit being from X through contact 39 to 10 through limit switch |29 to 13 through contact 35 to 30 through coil |32 to 3Ia, through protective resistance |33 to Y. The contact 36 of the stop relay 34, which is normally closed, opens when the above mentioned circuit is closed and thereby opens the low voltage relay circuit, dropping out the low voltage relay 31. The other of the two poles 3l of the stop relay 34 closes a circuit from X to 50 through the interlock 63, of the low 'voltage or 40 volt line contacter 6| to 5|',\ through the interlock 50' to 52 of the high voltage or 230 v olt line contactor 58 through dynamic braking ontactor coil 56- to Y, and provides the dynamic braking for the press by closing contacts 61 of the dynamic braking contactor 66, thereby closing a vcircuit through a resistance element |34, associated with each of the unit and folder motors I4 and |5, which shunts. the motor armatures from AI through selector 80 to 5, through dynamic contact 31 to Bl, through resistance element |34 to A2. Dynamic braking is accomplished by short circuiting the drive motor armatures through resistance element |34, and contacts 51 of contactor 6B whenever a stop button is depressed or an overload relay operates. A normally open interlock |00 operated by the dynamic braking contactar 66, connected across the exciter generator field rheostat |26 provides full eld on the vdrive motors for dynamic braking. No matter what operating position may be occupied by switch arm v |0| when interlock |00 is' closed, the generator 19 obtains full voltage from X through interlock |00 to f1 through segment |21, contact |05, and

the field of the generator 19 to Y. Since the mol tor fields 8| are excited in turn by the generator 19 they also have full eld provided for brak- K ing.7 The combination of a full ileld interlock to build up the generator voltage and in turn the generated armature voltage of the drive motors introduces a time element in the building up of the drive motor/ voltage, which tends to keep the current peaks toa minimum and holds the current practically constant over the braking peg, riod.

When the low voltage relay 31 drops out as the result of the depression of the stop button or the operation of the usual overload relay (not shown), the low voltage relay closes the decrease button circuit, causing current to ow from X through contact 3.9 of the low voltage relay 31 to 10, through the limit switch |29 to 13, through coil 52 to Y, thus closing contacts 53 of the decrease pilot motor relay. Theclosingof said contacts 53 causes current to flow fromX to 30 p through the decrease eld |3| and armature |00 of the pilot motor, causing the same effect as that caused by the depression of the decrease button, namely, the return of the arm |0| to normal or oil? position as above described.

`The circuit controlled by the paster button 3,4 is one ,of the usual'type, having the function of slowing down the press to permit making the paster, and need not be described in detail.

One difficulty in connection with dual voltage control for presses has been in transferring from the high voltage circuit to the low voltage circuit. To accomplish this we employ, in the connection presently described, a current rectier |35, which may be of any suitable type and is preferably a dry plate rectier, similar to those used in battery charging and rectifying units. This device prevents the low voltage contactor 6| from picking up or actuating after the high voltage contactor 58 drops out until the main motor counter E. M. F. is equal to the opposing voltage of the low voltage line. In the present embodiment wel accomplish this by connecting a protective resistance |33 (Fig. 2) across one pole 52 of the low voltage contactor 6| and across the other pole 62 of said contactor 5| connecting a relay coil |31,r the rectier |35 and an interlock |33, associated with the high voltage contactar 53. The

interlock |33 serves to keep this circuit open at all times except when the high voltage contactar is de-energized and to close the circuitthrough the above mentioned devices particularly during the period of transfer from high to low voltage. Closing of said interlock |30, which results from opening the contacter 58 while the press is running at high speed will establishva circuit from AI through the motor series ield, through the relay coil |31 to 3, through the rectier |35 to 3, through said interlock |30 to 2, through one pole of the low voltage switch 12 to through thelow voltage rgenerator armature circuit to through the other pole of the switch12'to l, through fthe' pgotective' resistance |36 to R, through the amature regulatingresistance 15, 14, and 13 and bats to the motor at A2.

If the main motor is' generating a counterl to\ the opposing low voltage circuit, nocurrent will flow through the relay |31 which permits the contacts |I4 thereof to close, and will in turn close the low voltage contactor 6|, and complete the low voltage power circuit to the press drive motorsgrthe transfer being made at a time when the counter E. M. F; is substantiallyequal to the low voltagey linecurrent.

In order to insure that the master switch arm |0| is in o position and that the control of the vstop button is absolute, so that once the stop button has been pressed, especially in emergency, it will be impossible for any person not knowing of the emergency to control .the press from any of .the press units, we provide means for interlocking the low voltage'relay and the stop'relay circuits upon manipulation of the stop button so that each provides a holding circuit for the other, thus pre-v at the off position. To accomplish this, the back contact 33 of the stop relay 34 is connected in series with the coil winding of V the low voltage relay 31, and the back contact 39 of the low voltage relay 31 is connected in series with the d'ecrease limit switch |29, one of the poles 35 and the coil |32, of the stop relay 34 and the protecting resistance |33. 'I'he decrease limit switch |29 isopened by the arm |0| in arriving at the oi position thus opening the interlocked circuits. 'I'he opening of said limit switch |29 opens the circuit from X through contact 39 to 10 through limit switch |29 to 13, through contact 35 of stop relay to 30 through stop relay coil to 3|, through protective resistance |33 to Y, thus de-energizing coil |32, thus opening one polel 35 and closing the aoraeei attendant advantages will be understood from the foregoing description, and it will be apparent that .various changes may be made in the form, construction and arrangement of the parts without departing from the spirit and scope of the invention, or sacricing all of its material advantages, the form hereinbefore described being merely a preferred embodiment thereof.

We claim:

l. In a control system for printing presses or the like, a high voltage circuit for operating speeds, a low voltage circuit for slow speeds, a motor operated on said circuits, contactors for closing said high and low voltage circuits respectively, and means operative upon opening of the high voltage contactor for opposing the incoming voltage of the low voltage circuit with the counter E. M. F. generated by the motor whereby to prevent closing of the low voltage circuit after operation of the motor onvthe high voltage circuit until the counter E. M. F. generated by the motor reduces to substantially the opposing E. M. F. of the low voltage line.

2. In a control system for printing presses or the like, a high voltage circuit for operating speeds, a low voltage circuit for slow speeds, a motor operated on said circuits, contactors for closing said high and low voltage circuits respectively, and means for preventing the closing of the low voltage contactar after operation of the motor on the high voltage circuit until the counter E. M. F. generated by the motor reduces to substantially the opposing E. M. F. of the lov; voltage line, saidmeans including a relay coil, a normally closed contact in the low voltage circuit adapted to vbe opened by energizing said coil, and means for directing the incoming voltage of the low voltage circuit through said coil in opposition to the counter E. M. F. generated by the-motor.

3. In a control system for printing presses or the like, a high voltage circuit for operating speeds, a low voltage circuit for slow speeds, a motor operated on said circuits, contactors for closing said high and low voltage circuits respectively, and means for preventing the closing ci the low voltage circuit after operation of the motor on the high voltage circuit until the counier E. M. F. generated by the motor reduces to substantially the opposing E. M. F. of the low voltage line, said means including a rectiiiei through which the current may pass from sa'id\.

motor in the direction of the counter E. M. F., but not in the opposite direction li. In a control system for printing presses or the like, a high voltage circuit for operating speeds, a low voltage circuit for slow speeds, a motor operated on said circuits, contactors VJfor closing said high and low voltage circuits respectively, and means for preventing the closing of the low voltage circuit after operation of the moto-r on the high voltage circuit until the counter E. M. i?. generated by the motor reduces to substantially the opposing E. M. F. of the low voltage line, said means including a relay coil, a

normally closed contact in the low voltage circuit adapted to be opened by energizing said ooit-and a rectifier through which the current generated by the motor may pass to energize said coil so long as the counter E. M. F. is in excess of the E. M. F. opposed to it from the low voltage line, said coil being deenergized when said counter E. M. F. is substantially equal to the E. M. F. oi the low voltage line, thereby permitting the low voltage circuit to be closed.

5. In a control system for printing presses or the like in which a plurality of drive motors are employed for operating the units and folders of the press, an exciter generator for supplying a control current to the elds of said motors, a rheostat for adjusting the generator voltage, a dynamic braking contactor, and an interlock actuated by said dynamic braking contacter for building up the generator voltage as the press speed decreases thus maintaining a substantially uniform dynamic braking current in the drive motor armature during the braking period.

6. A controller for printing presses or the like comprising in combination with a plurality of motors for driving the units and folders of the press, an exciter generator for supplying a control current to the elds of said motors, a master switch for controlling all of said motors, said switch being movable through a plurality of operative positions, means including a stop button for stopping the press, and means whereby press control is prevented after the stop button has been actuated until said master switch has been returned to its initial position.

7. A controller for printing presses or the like comprising in combination with a plurality of motors `for driving the units and folders of the press, an exciter generator for supplying a control current to the elds of said motors, a high voltage circuit for operating the motors at high speed, a low voltage circuit for low speeds, a low voitage'reiay and circuit, a stop relay and circuit, push button stations including stop buttons associated with the press units, means operable upon manipulation of any stop buttons for interlocking the low voltage relay and stop relay circuits, causing each to provide a holding circuit for the other, thereby preventing control of the press, a master switch including an arm movable through a vplurality of operative positions, and means operable only upon the return of said arm to initial position for releasing said interlocked Circuits to permit further control of the press from the push button stations.

8. A controller ror printing presses or the like comprising in combination with a plurality of drive motors, a master control device including a field exciter for varying the field strength of said motors simultaneously, a plurality of sources of voltage for said motors and control devices whereby a low voltage may be employed for slow running of the press, as for plating the cylinders or threading the paper, and whereby high voltage may be employed for operating speeds, said motors being subject to control by said master control device when operating on either nigh or low voltage.

9. in a control system for printing presses or the like, a high voltage circuit for operating speeds, a low voltage circuit for slow speeds, a motor operated on said circuits, contactors for closing said high and low voltage circuits re spectively, and means for preventing the closing or the low Voltage circuit after operation ci the motor on the high voltage circuit until the counter E. M. F. generated by the motor reduces to substantially the opposing E. M. F'. of the low voltage line, said means including a control relay for the circuit oi' the low voltage contacter,

'and an energizing circuit for said relay connected in series with the motor, said circuit including a rectier arranged to alloW said relay to become energized to hold the low voltage contactor open -so long as the voltage of the current generated by thevmotor exceeds the voltage opposed to it from the low voltage line.

10. In a control system for printing presses or the like, a high voltage circuit for operating 5 speeds, a low voltage circuit for slow speeds,4 a motor operated on said circuits, contactors for closing said high and low voltage circuits respectively, and means for preventing the closing of the low voltage circuit after operation lu of the motor on the high voltage circuit until the counter E. M. F. generated by the motor reduces to substantially the opposing E. M. F. of the low voltage line, said means comprising a relay including a coil and a normally closed con*- l tactor for controlling the circuit which energizes so long as the voltage of the current generated by the motor exceeds the voltage opposed to it from the low voltage line.

` HAROLD L. MCCLEERY. z J. CLINE. 

